Artificial molar teeth



April 1951 R. o. DICKSON 2,548,956

ARTIFICIAL MOLAR TEETH Filed Aug. 8, 1947 INVENTOR. nos: 0. o/cwso/w ATTORNEYS,

ments.

Patented Apr. 17, 1951 UNITED STATES PATENT OFFICE ARTIFICIAL MOLAR TEETH Ross 0. Dickson, Mexico City, Mexico Application August 8, 1947, Serial No. 767,561

1 Claim. 1

v This invention relates to improvements in artificial teeth (bicuspids and molars), and particularly concerns the disposition of the occlusal surfaces in reference to the cusps, bearing surfaces, spillways, cutting edges, and ridges.

Artificial teeth at present in use may be roughly divided into two classes, the anatomical, simulating natural teeth, and the mechanical, having occlusal surfaces provided with depressions or cavities of various shapes and arrange- The anatomical teeth have on their clusal surfaces irregular shaped, rounded cusps separated by fissures and are so arranged that the cusps on an upper tooth seat in the fissures in the meeting occlusal surface of a complementary lower tooth and the cusps on the lower tooth seat in the fissures in the corresponding upper tooth. This provides an extremely efficient cutting and grinding structure which, in the case of natural teeth, has no particular disadvantage. In the case of artificial teeth however, the interlocking of the cusps and complementary fissures of the upper and lower teeth tends to dislodge the dentures if the lower jaw or mandible is moved laterally relative to the upper jaw, as is necessary to produce a grinding action to prop- .erly masticate food. This causes the wearers of strain on the facial muscles.

In order to avoid this difiiculty dentists have deviced the so-called mechanical or cuspless type of teeth having substantially planar occlusal surfaces which can be moved laterally relative to each other while in contact with sufficient case that the dentures are not dislodged.

Obviously planar occlusal surfaces would have very little grinding or masticating efficiency so the designers of this type of teeth have provided the planar occlusal surfaces with recesses or depressions in the attempt to increase their masticating efficiency. Such recesses have been provided in the form of long, narrow, substantially parallel grooves, in some cases intersected by cross grooves, but such grooves have very little effect as they soon become clogged with partly masticated food which they are unable to discharge. Another attempt has resulted in the provision of a groove around the occlusal surface within the margin of such surface and a notch leading from this groov to the lingual side of the tooth. Such a groove also clogs and this .then be designated as flat cusps.

construction has likewise been found too inefficient for satisfactory use. Still another attempt has resulted in the provision of spaced apart depressions of geometric, usually triangular, shape in the occlusal surfaces, such recesses having inclined bottom walls making them V-shaped in cross section. Such grooves or recesses also quickly fill up with compacted food as they are not cleaned by complementary cusps as in the case of natural or artificial teeth.

Both the cusped or anatomical teeth and the cuspless or mechanical teeth thus have serious disadvantages in use. It is conceived however, that teeth having the easy sliding facility of the mechanical type and, at the same time, the self-cleaning facility of the anatomical type would substantially overcome the major difiiculties of the two present types or classes of artificial teeth. Such a tooth may be designated a flat cusp tooth. V For the purposes of the present description a cusp 'may be defined as a projection on the occlusal surface of a tooth, such projection being confined to one portion of the tooth, having a an area which is a fraction, less than of the area of the occlusal surface, and is surrounded by steep sides and separated from other cusps of the same tooth by fissures or grooves.

At the time or eruption, natural teeth have sharply pointed cusps but during use these points wear down to a rounded shape and finally to substantially fiat surfaces and the cusps'may Even such fiat cusps will interlock to a limited extent in the corresponding fissures or depressions but,

because of their shape and the shape of the corresponding fissures the self-cleaning facility of even worn natural teeth is maintained.

Th present invention contemplates the provision of artificial teeth having the fissures or depressions, also referred to as canals or spillways, so shaped as to provide an adequate selfcleaning action and having the cusps flattened and shaped, and in some cases interconnected by ridges, to subsubstantialy eliminate themterlocking of the cusps in the associated fissures or depressions. In this case an adequate and efiicient grinding action is obtained between the cusps and ridges of complementary upper and lower teeth and an effective cutting action is obtained from the shearing effect between the edges of the cusps of the complementary upper and lower teeth.

A principal object of the present invention is thus to provide a set of artificial'teeth having lower second bicuspid il.

anterior; posterior, or-,lateral,-without the cusps interfering, as in present constructions of anatomical artificial teeth. Each upper molar tooth has spaced-apart cusps and an angular, longitudinally extending ridge which passes lingually,

buccally and buccally lingually over spaced-apart cusps and a longitudinally extending, straight ridge of the complementary; inferiorlmolar so that the edges of the cusps and ridges shear, the food. The masticated food escapes through the depressions or food canals buccally and lingually, being moved outwardly of these canals by'the relative movement of the cusps of occluded upper and lower teeth, thus permitting the cutting edges to contact more efficiently. In the present invention, the fiat cusps become bearing surfaces and are separated by the canals or spillways which receive the food after being cut or ground and open freely to the sides of the teeth. As the food is caught in the grooves of the superior teeth, it is cut by the sharp edges of the cusps and central ridges of the inferior teeth, as the latter pass the sharp margins of the superior grooves, thus cutting, grinding and disposing of the food more efficiently and maintaining the occlusal surfaces of the teeth free of compacted food.

The foregoing and other objects and features of the invention will be made fully apparent to those skilled in the art from a consideration of the following detailed description taken in conl junction with the accompanying drawings, in

"which:

larged scale taken-on the line V-V of- Figure 1.

Figure 6 represents aplan view of'a lower bicuspid.

Figure '7 is a bottom plan view of an upper bicuspid.

Figure 8 is a view corresponding to Figure 3 of a slightly modified form of the upper molar.

Figure 9 is a view corresponding to "Figure 4 of a slightly modified form of the lower molar.

Referring to the drawings, and firstto Figures l and 2 thereof, the teeth there shown comprise an upper first molar I, an upper second molar 2, an upper first bicuspid 3, an upper second bicuspid t, a lower'first molar 5, a lower second molar 6,-a lower first bicuspid 1, and a The arrow D points to the distal and the arrow M points toward the mesial ends of the dentures.

It will be observed from these figuresthat all of said teeth have flat, occlusal' surfaces, and that the teeth are free from projections extending beyond such-flat or plane surfaces. 'I-he bearing surfaces, as will hereinafter be disclosed in detail, comprise the flat tops of cusps, and the fiat tops of cutting ridges connecting certain of the cusps, said cusps having intervening depressions or canals opening buccally and lingually to the sides of the teeth, the buccal side appearing in Figure 1, and the lingual in Figure 2. The areas and disposition of the occlusal surfaces relative to the canals and spillways are such that the cusps .cannot project into the depressions in any position of the man- I dible.

Throughout the drawings, reference numeral .lildesignates the buccal or outer, H the lingual or inner, 12 the mesial or front, and I3 the distal or rear faces of the teeth.

sion orfood-canal 18' between the cusps 14-..and

IT leading to the lingual faca a canal I91lbetween the cusps 'liand: I6 to the buccal face,-a canal 2Q between-the cusps l4 and 15 leading .to the distal face, and acutting ridge. 2| connecting cusps i4 and IT. The cutting ridge 2|.extends inwardly toward the center lineof the toothzpresentinga generally angular or :V-shaped': formation and the canal 29 extends adjacentand :parallelwith the-sides of the v vopposite' the canal I8. In this figure; as in Figures 7 and.8, the central line of the upper teeth-isindicated by X1.

In Figured, the lower molar 5 thereshownis providedwith aflat mesial lingual cusp 1.4a, and a mesial buccal cusp l5a, a distalbuccal cusp ifia, a distal lingual cusp ila, a.-foodz.canal 18a between the cusps 14a and Ilaileadingctoxthe lingual face of the tooth, a food canal Embetween the cusps 15a and [6a leading :to the buccal face. A central ridge-20a extendshfromalocation between the cusps I laand: l5a zlongitudinally of the tooth, between' the cusps 16a and Ila and to the distal orrear face of: the'tooth. :A short canal 27 between cusps 16a andi-thedistal end portion of ridge Zilaopens to the distal face, and a short canal 29 between the-cusps l lwand the ridge alsoopensto the distal faceofthe tooth, and'a distal wedge-shaped central-cusp. 22a. ?'In this figure andin' Figures 6 and 9, the line X2 .indicates the central I line of the teeth.

In- Figure 5, the :upper molar l-is= shown-s in normal relation-to the lower-'molari. The cusps M and [5 of the upper are inocclu'siom'respectively,-with the cusps 14a, and lfiaof' thelower, the distal portions of the superior cusps extending over the canals IBa and- 19a, respectively; of the inferior molar. "The longitudinal canalflfl of the superioroverlies' the' central cutting ridge 20a of the inferiorpand it will belseensthakon relative movement of Jthexteeth in. any: direction, the same remaining :occluded,".at shearing:.action will-be obtained. :It will also be notednthat :the food canals are :ofi-shaped=crosscsection: and open directly to thee sides :-of the i teeth; so. :the

- masticated food-will continuouslypass outwardly of the teeth throughitheseieanals andnwill. not pack in the canals ondepressions. :Theaselfcleaning facility 1: of i the cteeth is :;thus maintained.

i The construction ofiithe: .lowerand: upper-,-.:bi:- cuspids as "shown; in Figures 6 and 7; respectively, is analogous: to that of the lower. and ;uppermo- :lars of Figures 4: and13,--.respectively; in that :the cusps. arealliflat; the occlusala surfaces lyingqin asingleplane; the; cusps-and cutting ridges being flush with each other and divided in the central line by longitudinal grooves in the superiors which function over the central cutting ridges of the inferiors. Referring to Figure 6, the lower bicuspid shown is provided with a food canal 23a, which runs generally parallel with the central ridge 25a. The lingual cusp 24a, and the buccal cusp 25a are both flat with their surfaces lying in the same plane. A short distal canal to the buccal side of the tooth is provided at 27c, and a depression 28a on the first inferior bicuspid functions as a spillway for the second bicuspid.

In Figure 7, the upper bicuspid corresponding to the lower of Figure 6 is shown and comprises a lingual cusp 24, a buccal cusp 25, and a 1ongitudal canal 23 between the two cusps.

In the slightly modified form shown in Figure 8, the ridge 2lb connects the cusps Mb and [6b rather than the cusps corresponding to Hi and H of the form shown in Figure 3. This ridge thus interrupts the canal 20b. Otherwise correspondence between the parts numbered Mb, I51), and so forth, and the parts numbered l4, l5, and so forth, of the previously-described forms will be apparent. The lower molar shown in Figure 9 corresponds to that shown in Figure 4, except that the two spillways 180 are provided to the lingual side of the tooth. Otherwise, the correspondence between the parts numbered I40, I50, and so forth, and theparts numbered Ma, I5a, and so forth, of Figure 4, will be apparent.

It will be noted that in all the occlusal surfaces of these molar teeth, the cusps and cutting ridges are flush one with another, and that the cutting margins of the cusps and ridges are so arranged that the opposing margins pass over them with a shearing or scissor-cutting action as they pass each other with any movement of the mandible forward, backward, laterally, or rotary, the food being dropped in the spillways between the teeth and in the teeth for disposal.

While there have been herein described certain preferred embodiments of the invention, other embodiments within the scope of the appended claims will be fully apparent to those skilled in the art from a consideration of the forms shown and the teachings thereof.

I claim:

In a group of artificial teeth including complementary lower and upper teeth having meeting occlusal surfaces of planar formation, a lower tooth having in its occlusal surface depressions opening to the sides of said tooth and defining four fiat topped cusps respectively disposed at the mesial-lingual, distal-lingual, mesial-buccal and distal-buccal corners of the tooth and a narrow ridge extending from a location between the mesial lingual and mesial buccal cusps, between the distal lingual and distal buccal cusps to the distal end of the tooth, and a complementary upper tooth having in its occlusal surface depressions opening to the sides of the tooth defining four fiat topped cusps respectively disposed at the mesiallingual, distal-lingual, mesial-buccal and distalbuccal corners of the tooth, and a narrow ridge extending from the mesial-lingual cusps to a location adjacent the center of the tooth and from such location to the distal-lingual cusps, and roviding a groove between said ridge and the mesial-buccal and distal-buccal cusps.

ROSS O. DICKSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,837,042 Hall Dec. 15, 1931 1,879,419 Myerson Sept. 27, 1932 2,141,487 Pleasure Dec. 27, 1938 2,195,370 La Due Mar. 26, 1940 2,404,327 Tighe July 16, 1946 

